The present invention is directed to an improved carbon electrode for use in a carbon arc lamp, particularly of the type used for weathering testers.
There are known weathering testers of the carbon arc lamp type wherein a plurality of carbon electrodes are grasped in a bottom holder which is connected to an electric source, and wherein a further plurality of carbon electrodes are held by an upper holder. The two holders are moved toward and away from each other by suitable means to permit discharge between the two groups of carbon electrodes. Samples to be subjected to weathering tests are placed around this type of arc lamp.
Known carbon electrodes employed in such devices generally have a uniform outer diameter and are comprised of carbon having a central core of a suitable luminous agent and an outer coating of a suitable metal such as copper or aluminum. When such carbon electrodes are attached to a lower holder and the lamp is discharged during use, ashes, molten oxides and molten metal will fall downwardly onto the lower holder. This results in corrosion of the contact parts of the lower holder with the obviously undesirable further result of poor quality electrical contact.
Past attempts to correct this problem have necessitated the complicated fabrication of devices such as shields to prevent such corrosion.